Slideshow: New Carbon Composites for Volume Car Production

The JEC Europe 2014 composites show in Paris last month was a chance for many companies to showcase their carbon fiber composites and related products, especially for volume automotive manufacturing. Several companies that attended (and others that didn't) touted their contributions to BMW's all-carbon composite body-in-white. Others introduced new automotive carbon composite products and processes.

This rear seat base was produced via the resin transfer molding (RTM) process using Dow's commercial Voraforce 5300 epoxy carbon composite. The demonstration part, produced by Fehrer Automotive as part of Dow's Voraforce development program, is 60% carbon fiber by weight. In structural applications, one complex composite part can replace several pieces of steel welded together. The material's low viscosity, low moisture absorption, and cycle time of less than 90 seconds can make carbon composites used for such parts more price-competitive with steel in high volumes.

(Source: Dow Automotive Systems)

One of the most significant introductions at JEC Europe was the commercial production launch of Dow's ultra-fast Voraforce 5300 matrix. The product is aimed at resin transfer molding (RTM) processes for making structural parts for high-volume car production. We've been telling you about advances in this material since 2012, when Dow established a carbon fiber source in Turkey. More recently, in a slideshow, we detailed how Dow has been tailoring the material and the process to address its OEM car maker customers' goals.

Peter Cate, global strategic marketing manager for Dow Automotive Systems, told us the commercial product has the same fast cycle time of less than 90 seconds, which you can see in this video. It also has a processing viscosity of 15 millipascal seconds (mPa.s), compared with the typical competitive viscosities of 50-70 mPa.s, along with low moisture absorption.

Cate said that competitors often talk about cure times of 2-3 minutes but not about overall cycle time, which also includes loading time. In the video, Dow's system achieves an 80-second cycle time, including a cure time of only 40 seconds. The carbon composite material is based on epoxy, not polyurethane (PU), which some RTM competitors use. "From published data, we see that PU RTM systems have a higher viscosity in comparison to our Voraforce 5300, between 30 and 40 mPa.s," he said. "But the real issue is not only low viscosity, but how long that can be maintained while still preserving a fast cure time."

To maintain a low enough viscosity for getting excellent wetting of the fiber pre-form in RTM systems, processing temperatures for PU must be low, but that results in a total molding cycle time of around five minutes. For epoxy, which has been used for a long time in aerospace carbon fiber composite manufacturing, lowering temperatures isn't required. The key, Cate said, is balancing infusion against cure, which epoxy provides.

"We make both polyurethane and epoxy, so we're process-neutral," he said. "We've challenged our polyurethane R&D engineers to match what we've done with epoxy -- we'd be happy if it could do the same." PU has a few other shortcomings: It needs to post-cure in an oven, it doesn't have the same range of possible fiber sizing, and it's not moisture-resistant.

Thorough wetting and filling is key for making the large structural parts that auto OEMs want and for consolidating several parts into one large one. This is also important for making accurate cost comparisons. Carbon composites are more expensive in a 1:1 material cost comparison of so many square meters versus the same amount of steel, Cate said. But processes and design of parts can change that ratio. If one large, complex composite part can be made quickly and in high volumes, versus several steel parts welded together, costs are much more competitive.

I do not understand the persistance of the myth that automobile manufacturers design cars to fail. I am not aware of any manufactured good, from any source, made out of any material that lasts forever. In the case of motorized vehicles, many times they are traded in simply because the owner just wants a change. I look around my house and see that I no longer have the same furniture, dishes, appliances, flatware, ad infinitum, yet I am told that the reason I no longer drive my 56 Chrysler is because it was designed to be disposed of and replaced. What about everything else. Is that all some sort of master plan as well? Even stones eventually wear away from weather, but cars are supposed to last forever.

As far as the acceptance of composites goes is it not possible that many times it is just appearance and feel. I am a fisherman and love the lightness and action of my composite rods, but just do not care for reels of the same construction. I am sure they perform well, but I do not like the look and feel.

bobjengr, you're certainly right about the amount of R&D and testing that's gone into all these carbon composite materials. I think we're approaching what market analysts like to call an inflection point, aka a tipping point, where several factors come together very quickly to send a technology over a hump and into the next stage, usually one of very fast expansion and wide adoption.To me, it's interesting that a parallel move is going on with 3D printed versions of the (more or less) same stuff.

I think these developments are very significant due to RoHS requirements and bio-degradable needs developed by the EU. I am positive a great deal of R&D went into formulation of the material composites and testing relative to application needs. Lighter yet stronger are definitely desirable if achieved at a price point that can be absorbed AND deliver a payback relative to the investment. Again, we see this technology is evolutionary as opposed to revolutionary. Great post Ann. Thank you for keeping us informed.

That '10%' comes at a great cost and is only of the unibody part. But of the whole velicle you have to double + the price for 20 less pounds. Sorry but those pricepoints for CF just don't work in cars.

Vs medium tech composite that costs l0% of a similar CF unit that weighs 50% less than a steel or alum one. Which do you think will actually get built for regular people? If CF units don't get built because too expensive, how will they help CAFE?

But wouldn't a 50% weight medium tech car that costs less to build as a steel one sell much better, have a bigger effect on CAFE?

And the CF advantage depend on getting the layup right as any mess up of too much resin, etc kills the advantage of lighter weight, no? Thus why Boeing trashed $1billion of CF parts for the 787, No?

once again, that is incorrect. a carbon bike frame gets damaged, you repair it. turns out that carbon fiber lends itself to repair much more than metal frames. you can repair the local area instead of the entire tube.

calfeedesign.comspydercomposites.comconcept2composite.com

racecar chassis can often take repairs as well. this is besides the fact that the type of crash that damages one would have destroyed a steel spaceframe. keep in mind that the crash stuctures are separate, bolt-on parts, as they should be.

quotefrom http://www.sauberf1team.com/en/car/technology-materials/

"Their extremely high strength means that monocoques provide drivers with maximum protection even in major accidents. Because the fuel tank is also contained within the monocoque, dramatic accidents involving fires are a thing of the past. After a crash, the safety cell can almost always be repaired."

Good points all. The company that invests in new materials and processes may come out the winner. With carbon bikes if the frame is cracked you purchase a new one. If a race car is in a wreck you replace it. If your car is stressed it has to be replaced. So what? So out of all the cars made some are wrecked and replaced instead of everyone being repairable and most being destroyed when by obsolensce and normal wear and tear (and rust) render it unusable or desirable. Weight iand impact work against carbon fiber. so design out the weight and put on the tallest - not wide - wheels possible and maybe only three to eliminate 1) the weight of the forth and 2) the suspension dynamics that the forth creates. Oh, but you could only haul one person in a three wheeler, okay most of us travel most of the time solo. Cars were a cool oddity in 1900, never to totally replace horses. Transportation need a fundamental shift today that may be as big as the introduction of the model T. Engineers should lead the way. Get marketing and accounting out of the way for a while.

Good points all. The company that invests in new materials and processes may come out the winner. With carbon bikes if the frame is cracked you purchase a new one. If a race car is in a wreck you replace it. If your car is stressed it has to be replaced. So what? So out of all the cars made some are wrecked and replaced instead of everyone being repairable and most being destroyed when by obsolensce and normal wear and tear (and rust) render it unusable or desirable. Weight iand impact work against carbon fiber. so design out the weight and put on the tallest - not wide - wheels possible and maybe only three to eliminate 1) the weight of the forth and 2) the suspension dynamics that the forth creates. Oh, but you could only haul one person in a three wheeler, okay most of us travel most of the time solo. Cars were a cool oddity in 1900, never to totally replace horses. Transportation need a fundamental shift today that may be as big as the introduction of the model T. Engineers should lead the way. Get marketing and accounting out of the way for a while.

William K,you are so off the mark. many bicycle frames and wheels are made of carbon fiber. this includes mountain bikes, cross-country, enduro, downhill, and everything in between. they are extremely tough when designed right, even on impacts. some of the most impact resistant wheels for mountain bikes are carbon. and guess what? when they do yield, they dont "shatter". you get a small crack, which often takes weeks or months to even be noticed, much less make any difference. their structural performance far exceeds what can be made of the best aluminum alloys, steel, titanium, magnesium...

not all carbon fiber is brittle. some of the higher modulus fibers are, especially pitch-based fibers. others are high-resistance. you could tie them in a knot.

f1 and other motorsports crash structures are made from carbon fiber. these are FIA mandated parts, standardized with known properties. they could make them out of any material and require them to be used. they are made of carbon fiber.

J.D. One other place where a carbon fiber composite material presents a real challenge is in a high performance bicycle frames and wheels. They are probably fine for racing on smooth tracks and such, but in the real word bikes get abused by the places that they are ridden, and sometimes they bend a bit.A steel bike can be bent back into reasonably close shape right on the trail, while if a carbon bike did ever bend a bit it would be broken and need to be carried out, since it would probably not be rideable. And carbon fiber rims would be even worse, since not only would they break under impacts that would simply bend the steel rim, but they would be totally unfixable. Once again, smooth track racing only.

University of Southampton researchers have come up with a way to 3D print transparent optical fibers like those used in fiber-optic telecommunications cables, potentially boosting frequency and reducing loss.

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